The effects of buoyancy ratio on unsteady double-diffusive natural convection in a cavity filled with porous medium with uniform and non-uniform boundary conditions are analyzed in this paper. It is assumed that the left vertical wall and bottom wall are heated and concentrated (uniformly and nonuniformly), while the right vertical wall is maintained at a constant cold temperature, and the top wall is well insulated. The governing equations are solved numerically using a staggered grid finite-difference method to determine the streamlines, isotherms, isoconcentrations, local Nusselt number, local Sherwood number, average Nusselt number and average Sherwood number for various values of buoyancy ratio and Rayleigh number. The change of flow patterns with respect to time depicted and described here. The results are compared with previously published work and excellent agreement has been obtained. (C) 2015 Elsevier Ltd. All rights reserved.